1. Field of the Invention
The present invention generally relates to a white light LED (light emitting diode), and more particularly, to a white light LED with quantum well structures and manufacturing method thereof.
2. Description of Prior Art
White light LED will no doubt be replacing traditional light source, such as the incandescent lamp, for realizing the objective of saving energy. FIG. 4 depicts a variety of conventional white light LEDs. The conventional technologies regarding manufacturing white light LEDs can be categorized into several groups as follows:
1. Di-chromatic light source, as shown in 1, 2 and 3 of 4(a) in FIG. 4:
Example 1 of 4(a), using a blue light luminous element and a yellow light luminous element to generate the blue and yellow lights and mixing the lights to produce white light;
Example 2 of 4(a), using a blue light luminous element to excite the yellow phosphor to generate the blue and yellow lights and mixing the lights to produce white light; and
Example 3 of 4(a), using a dual-wavelength chip of blue light and yellow light to generate the blue and yellow lights and mixing the lights to produce white light.
2. Tri-chromatic light source, as shown in 1, 2 and 3 of 4(b) in FIG. 4:
Example 1 of 4(b), using a red light luminous element, a blue light luminous element and a green light luminous element to generate the red, blue and green lights and mixing the lights to produce white light;
Example 2 of 4(b), using a red light luminous element and a blue light luminous element to excite the green phosphor to generate the red, blue and green lights and mixing the lights to produce white light; and
Example 3 of 4(b), using a UV light to excite the red, blue and green phosphors to generate the red, blue and green lights and mixing the lights to produce white light.
3. Tetra-chromatic light source, as shown in 1, 2 and 3 of 4(c) in FIG. 4:
Example 1 of 4(c), using a red light luminous element, a blue light luminous element, a green light luminous element and a cyan light luminous element to generate the red, blue, green and cyan lights and mixing the lights to produce white light;
Example 2 of 4(c), using a red light luminous element, a blue light luminous element and a cyan light luminous element to excite the green phosphor to generate the red, blue, green and cyan lights and mixing the lights to produce white light; and
Example 3 of 4(c), using a red light luminous element and a blue light luminous element to excite the green phosphor and cyan phosphor to generate the red, blue, green and cyan lights and mixing the lights to produce white light. Alternatively, using more of different light sources to mix thereof to produce white light also can be considered.
The method of the di-chromatic light source has advantages of simplicity, stability and high luminous efficiency but has the drawback of low color gamut. The example 3 of the tri-chromatic light source has advantages of stable white point and large color gamut but has drawbacks of light leakage and yellowing phenomenon. The example 1, 2 of the tri-chromatic light source, the methods of the tetra-chromatic light source and more light sources have advantages of large color gamut and tunable white point but has drawbacks of complex driving circuits, color shift due to temperature and aging.